Unable to Select Champion BUG In Lobby - 2x Games In A Row (Plat Promos)

Hi fellow Leaguer's and Riot team:

Twice in a row my client didn't register my ban and/or lock-in choice even though I selected the champ at like 28 seconds and spammed "BAN" or "LOCK IN" like a fiend until 0 seconds. As usual, my selection was not being registered and I just failed my Platinum 5 promos because this happened 2x in a row during my series, and now I have a 30 minute queue timer because apparently I'm "dodging".

http://i.imgur.com/4CROTbL.png

Yes, my client is already on "low-spec" mode despite having a $2,000 machine and a solid connection. Anyone have any advice on how I can prevent this from happening? It has happened before, and now that the legacy client is officially retired, I have no other choice. This really upset me and I want to prevent it from EVER happening again.

Thank you.